The Erken laboratory established by Wilhelm Rodhe in 1946 celebrated its 50th birthday by a two-day seminar. The papers presented on this occasion were now published in Advances of Limnology No. 51. The publication gives an overview of current limnological research performed at the Erken laboratory. A number of intake studies are presented and other contributions were prepared for this issue. This is a most interesting summary of the activities of the laboratory and other papers presented at the symposium.